That's pretty much true. Amazon handles billing for millions of customers without any problems. It's overwhelmingly likely that the poster made an error somewhere in configuration or left a service running. We've had such an experience (somebody started a huge instance for a test and forgot to turn it off), Amazon's tech support was extremely considerate and refunded us most of the price.
And if you want to run large clusters on Amazon - feel free to try our software:
https://clusterk.com/ We can utilize Amazon's spot market with the resulting computation prices only slightly more expensive than electricity needed to run them.